1. Field of the Invention
The present invention relates to a control system, particularly to a control system for cigarette making and packaging systems.
2. Prior Art
In a system in which a cigarette making machine is operatively combined with a cigarette packaging machine, stopping of one machine may cause stopping of the other machine, resulting in low working rate or operation efficiency of the entire system. Further, restarting of the system often involves some troubles, such as unacceptable product quality, before smooth operation of the system is again established.
U.S. Pat. No. 4,149,545 discloses one type of system in which two cigarette making machines are interconnected to a single cigarette packing machine via a transfer system which uses individual conveyors to convey the cigarettes from each cigarette making machine to a single chute leading to the packing machine.
A series of switches are disposed along the conveyor in the transfer system. These switches actuate a control to slow down or speed up the packing machine in response to the amount of stored cigarettes. The packing machine is operated at a reduced half speed or at a full speed. However, with this type of transfer system, the speed of the packing machine is varied when the present reserve amount increases to a value above a predetermined upper limit or decreases to a value below a predetermined lower limit so that the reservoir will not be emptied of the stored cigarettes. Since the upper and lower limits are of fixed values, the system is not free from the problem that stopping of the making machines or the packaging machine may cause stopping of the packaging machine or the making machine.
U.S. Pat. No. 4,394,896 discloses another type of backlog control system, wherein the system lends itself to the use of manual control settings which, when taken together, form an optimum control pattern or "curve". This curve can be set into the system so as to take into consideration a nominal or optimum processing machine speed, a preselected rate of article supply to the system, a minimum and a maximum backlog and a threshold or "plateau" count wherein the processing machine speed remains constant over preselected variations in the present reserve amount. These control settings are introduced into the system as simple article counts and can be displayed as such at the controls. In other words, by merely setting in preselected article counts and other required settings an operator can, in effect, draw a "tailor made" control curve which represents various critical stages in the control of processing machine speed. However, the nominal or optimum processing machine speed, the minimum and the maximum backlog and the threshold count remain the same unless the operator operates the controls again.